Epilepsy is a common chronic condition disproportionately affecting children and which is often caused by brain insults that elevate extracellular neurotransmitter levels. My long-term goal is to elucidate fundamental pathological processes produced by such injuries in order to better understand the process of epileptogenesis and intervene with novel therapies. To this end, I have developed a new in vitro model which mimics such an initial insult and which produces persistent epileptiform discharges. In the proposed set of experiments, I will test the hypothesis that persistent hyperexcitability in this new model is due to decreased release of GABA by inhibitory interneurons. This hypothesis is based on my observations that: 1) the model produces persistent epileptiform discharges, 2) spontaneous inhibitory post-synaptic current (sIPSC) frequency is decreased compared to controls, and 3) sIPSC amplitude and decay kinetics are unaffected. Given these observations, I propose experiments which focus on pre-synaptic inhibitory mechanisms, as well as key alternative hypotheses. Using my model of early post-natal hyperexcitability, four Specific Aims will be addressed: 1) Characterize pre-synaptic inhibitory function. I will assess frequency, amplitude, and decay kinetics of sIPSCs, miniature IPSCs, and evoked IPSCs as well as GABA release probability. I will also determine expression levels of enzymes vital to pre-synaptic synthesis and packaging of GABA. 2) Characterize pre-synaptic excitatory function. I will determine glutamate release probability and assess miniature excitatory post-synaptic current frequency, amplitude, and decay kinetics. I will also determine expression levels of the enzyme responsible for pre-synaptic packaging of glutamate. 3) Characterize principal cell intrinsic properties and cell number. I will assess principal cell intrinsic properties using whole cell recording and count principal cells using quantitative stereology. 4) Characterize inhibitory interneuron intrinsic properties and cell number. I will assess I will assess inhibitory interneuron intrinsic properties using whole cell recording and count interneurons using quantitative stereology. I expect that these experiments will lead to translational research which improves treatment of children with epilepsy. [unreadable] [unreadable] [unreadable]